Oxygen transisition in lenses.

[Dave Dale]

At recent lens check at would the hospital I was 'told off'....I am not joking, for wearing my soft perm lenses!

The optican lady at the hospital said she hates them and would never fit them to anyone as the oxygen getting to th eeye through them is so poor that she has seen patients who have had new nerves growing into the cornea which has made a transplant later in life very difficult?

I only wear my softperms as the vison is far better than the RGP's, for whatever reason. Anyway, I take it I have no new nerves growing in my eye as she did'nt say when she looked!

Got me thinking now tho....

Cheers,

Dave.

[jayuk]

Hi

I wore them for about 2 years and agree they are excellent but this was back in 2001......

What she was reffering to was blood vessels growing into the cornea.....as opposed to nerves...in fact if she said nerves than id be a little scared as I dont think thats possible...but I could be wrong!

During the 2000-2002 period there was alot of concern with Softperms and the eyes oxygen uptake during its wear....BUT...I beleive this has been addressed with the new materials....and is not an issue now............

[John Smith]

Hello Dave,

It's probably blood vessels rather than nerves that could be growing into the cornea - these certainly do make a future transplant more awkward.

I think it is also true that soft lenses in general have lower oxygen permeability than RGPs - not sure where softperms fit on that scale though.

It does sound slightly like the optometrist's personal predudice against softperms though - you just have to go with what works! If you are worried about this though you could enquire about scleral lenses next time. They're quite comfortable and made of RGP material so have good permeability.

[Lynn White]

Dave...

John and Jay are right - she meant blood vessels not nerves and yes, I think her prejudices were showing lol...

The problem with soft lenses in general is although they do actually have a good oxygen permeability, because they cover the entire cornea and quite often "hug" the cornea, all the oxygen getting to the cornea has to go through the lens.

With RGP's, because the lens is smaller in diameter than the cornea, oxygen can get to the cornea round the edges of the lens, if you see what I mean. Because the RGP moves as well, oxygenated tears are moved around from outside the lens to under the lens.

This is why many professionals prefer RGP's. Soft lenses and soft perms have to rely on oxygen going through the lens itself only - as do sclerals actually. Scerals do have the advantage that there is usually an air bubble that gives extra oxygen to the eye.

In the end - what matters is your individual eye. If you get enough oxygen through your soft/softperm or scleral then thats OK. If you don't - then you have to consider RGP's...that is if you can tolerate them.

As ever its a balancing act!

Lynn

[John Smith]

...as do sclerals actually. Scerals do have the advantage that there is usually an air bubble that gives extra oxygen to the eye.

Hi Lynn,

I'll have to correct you there. Air bubbles under the scleral are a seriously bad idea. Firstly they interfere with vision, and secondly I've found that even a tiny bubble of air can cause discomfort after an hour or so of wear.

From the permeability point of view, then the cornea's oxygen would I suppose all come through the lens for a scleral wearer.

[Lynn White]

John...

OK

You correct me lol........ but I am only saying what is known as regards sceral fitting.

Gas permeability is such that originally oxygen was only transmitted to the eye through fenestrations ie holes drilled into the lens. The prescence of a bubble is actually what is worked for in a sceral fit - if you do not have this then you have touch down on the cornea.. not an ideal situation.

Nowadays, scerals are made of newer, gas permeable materials which do transmit oxygen through the whole lens. The major question is - is this enough to supply an eye with enough oxygen to survive without vascular encroachment - in simple terms - ingrowing blood vessels.

As I said - this is an individual and personal situation.

Lynn

[Dave Dale]

Yes...sorry she defo did say blood vessels to give her her due! Just my c**p memory.

Well thanks for informing me more guys, fore warned, fore armed and al that.

Yes and she did discuss the softperm working like a limpet (spl?) on the eye. I try to move the lens off my eye at least 3 times a day and put some refresh drops in....like a whale coming to the surface for another gulp of air!

Is this what occurs in diabetic people? I had a freind at work who went to have his vessels lasered every few months?

thanks again..another little worry disolved..

Dave.

[Lynn White]

This is nothing to do with diabetes.... that is a whole different ball game!

Diabetics can get extra blood vessels growing on the retina and have to have them lasered.

ingrowing blood vessels in the cornea will actually regress if you get more oxygen to the eye - so you don't need them lasering.

Lynn

[GarethB]

Air bubbles under the regular corneal RGP lens can be a problem too. The first fitting of my left lens ws comfortable, but on the check, it was noticed as I blinked, air bubles would form under the lens leading to 'dimple staining' on the cornea. The concern the optom had was that since I had had a corneal graft, the dimples could trap infection. Due to the ring on my cornea already fromt he graft looking like a crop circle once stained that too has the potential of trapping infection.

Since getting a larger lens for the left eye, all has been well until the eyelid had a reaction to some pollen that got stuck on the lens!

Doing well now, just resisting putting the lens in until the optom tells me to.

Gareth

[Sweet]

Just wanted to put something on diabetics, though i have no real idea on eyesight probs! LOL! But it does all come down to how well controlled it is and what treatment they are taking.

Obviously those who are diet controlled, or type 2 or NIDDM (Non-insulin deoendent) thereby taking tablets, are better off than those who are type one, obviously being insulin dependent! But again this still stands on how good blood sugars are. Consistenly high BM's cause damage to more organs than just your eyes, though this is a major problem for badly controlled diabetics.

LOL, also just a sidetrack, but advanced CRF (chronic renal failure) also causes blurred vision, although i guess with those with KC, i think that that will cause this before your kidneys do!! LOL!!!

Hehe, needing to go back to work now lol!!

Sweet X x X